The invention relates to an electrical protection apparatus, formed by association of a circuit breaker and an effector,
the circuit breaker comprising a first switch circuit with stationary and movable contacts, a mechanism controlled by an electromagnetic trip device with operating coil and by a thermal trip device, a pair of first and second arc guiding horns associated with a switching electrode, arranged near the contacts of the first switch circuit, an arc extinguishing chamber in the trip devices circuit, an input terminal, and an output terminal, PA1 the effector having a second switch circuit arranged to be electrically connected in series with said first switch circuit, when the latter is in the closed state, and to be automatically shunted by switching of the arc onto the electrode when the mechanism trips following a fault. PA1 the second switch circuit of the effector is connected to the stationary contact of the first switch circuit, and to said end of the coil, PA1 the insulating gap is shaped to enhance high-speed migration of the arc root onto the electrode when opening of the circuit breaker on a fault occurs and to guarantee the dielectric withstand in the closed state of the circuit breaker, and in the open state of the effector.
In a known apparatus of the kind mentioned, described in the document EP-A-104,981, the effector is formed by a static switch connected in series with the circuit breaker contacts. In a first embodiment, the switch is connected between the stationary contact and the input terminal, whereas the movable contact is connected to the output terminal by means of the thermal trip device and electromagnetic trip device. The switch is automatically shunted when the arc switches onto the lower guiding horn, which is permanently at the potential of the input terminal. To obtain high-speed arc switching, the connecting conductor extending the arcing horn to constitute the shunting circuit has to be placed as close as possible. The effect of proximity of this conductor enhances switching of the arc resulting in high-speed protection of the effector, but gives rise to problems of dielectric withstand when the circuit breaker contacts are closed and the switch is in the open state. In a second embodiment, the switch is connected between the trip devices and the output terminal, and the two are guiding horns are connected respectively to the input terminal and the output terminal. In the event of a fault occurring, shunting of the switch is established with a delay, for it is necessary to wait until the end of the opening travel of the movable contact of the circuit breaker to obtain switching of the arc onto the guiding horn which is at the potential of the output terminal.